Based on the percentages it's blatantly obvious which party was more in favor of civil rights for minorities, Republicans. So why would the Racist democrats, the ones that voted no, want to join the party that was much more unanimous than the party in which they currently reside? What you are saying is like Nancy Pelosi becoming a republican because Trump became a democrat. It's absurd. You've been taught a lie.
https://en.wikipedia.org/wiki/Civil_Rights_Act_of_1964
Okay... why did a Republican, nominee of the party "more in favor of civil rights for minorities," vote against the Civil Rights Act of 1964? And why did Nixon, a Republican, follow his lead in the following election, emphasizing law and order, an end to protests, and a war on drugs? Why did Strom Thurmond, a Democrat, join the Republican party?
Kennedy and Johnson were Democrats. The House and Senate were both Democratically controlled.
Saying that Republicans passed civil rights because there were 18 Southern Bloc Democrats who fought it in the Senate is just lying about the facts.